This is a proposal to study biochemistry and pharmacology of the retina with particular emphasis on cyclic nucleotides. The overall aim is to define the role of cyclic AMP in retinal function and metabolism. We will address and explore the hypothesis that retina contains cyclic AMP and cyclic GMP systems, each in different subcellular or cellular locations and each with different characteristics and functions. Utilizing quantitative histochemical methods and techniques we plan to identify, localize and characterize guanylate cyclases, adenylate cyclases, cyclic nucleotic phosphodiesterases and cyclic nucleotide-dependent protein kinases in retina. Regional purine nucleotide metabolism in retina also will be evaluated. In addition, we wish to define what factors (i.e., light, neurotransmitters, ions, cellular depolarization) regulate cyclic nucleotide levels in retina and explain their mechanisms. This project, which correlates retinal biochemistry and morphology, should help explain some molecular mechanisms underlying vision.